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Network Mirror Mode replays the parent network’s real blocks onto a Virtual Environment. When the Virtual Environment is forked at a past block, that replay covers real history: every mainnet transaction from the fork point onward re-executes on your private copy, in order. This how-to uses that replay to backtest a position: fork at a past date, acquire a yield-bearing token, replay history forward, and read the yield the position actually earned over the period. The worked example is the Franklin OnChain U.S. Government Money Fund token (BENJI) on Ethereum Mainnet. The same workflow applies to any yield-bearing token.
Network Mirror Mode is available on the paid plan. To enable it for your account, contact our sales team.

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Practical notes

  • Yield appears when the fund’s real yield transactions replay. A rebasing token’s held balance grows automatically. For a fund that distributes to registered holders, track a holder position so the distributions land on it.
  • Cheatcodes pause with sync. Do all setup (funding, entering the position) while sync is paused, then start the replay.
  • One network per environment. Network Mirror Mode runs against a single parent network; it isn’t combined with multichain Virtual Environments.
  • Replay is bounded by real blocks. Covering a long period means replaying many blocks. To capture yield quickly, fork shortly before a known distribution, or replay a representative window and annualize.

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Next steps

  • Track a storage slot instead of a balance (State drift → State → Track variable) to follow any contract variable over the replayed period.
  • Point a dapp’s RPC at the Virtual Environment to drive the same replay from your own UI. See Stage dapps.
  • Read the Network Mirror Mode concept page for sync mechanics, time controls, and cheatcode behavior.